Fluid-ejecting integrated circuit utilizing electromagnetic displacement

ABSTRACT

A fluid ejecting integrated circuit includes a wafer substrate. A drive circuitry layer is positioned on the wafer substrate. A protective passivation layer is positioned on the drive circuitry layer. A nozzle chamber wall extends from the passivation layer and a roof wall is positioned on the nozzle chamber wall such that the nozzle chamber wall and the roof wall define a nozzle chamber and a fluid ejection port in fluid communication with the nozzle chamber. A fluid ejecting member overlies the passivation layer within the nozzle chamber and is configured to be displaced to eject fluid through the fluid ejection port. A pair of spaced apart electrodes is connected to the drive circuitry layer so that the drive circuitry layer can create a potential difference between the electrodes, with one of the electrodes fast with the fluid ejecting member to displace the fluid ejecting member as a result of the potential difference.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No. 10/957,718 filed on Oct. 5, 2004, which is a continuation of U.S. application Ser. No 10/184,883 filed on Jul. 1, 2002, now issued as U.S. Pat. No. 6,820,968, which is a continuation of U.S. application Ser. No. 09/113070 filed Jul. 10, 1998, now issued as U.S. Pat. No. 6,476,863, the entire contents of which are herein incorporated by reference.

The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their US patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority. US Patent Application Cross-Referenced (Claiming Right of Priority from Australian Australian Provisional Provisional Patent No. Application) Docket No. PO7991 6750901 ART01US PO8505 6476863 ART02US PO7988 6788336 ART03US PO9395 6322181 ART04US PO8017 6597817 ART06US PO8014 6227648 ART07US PO8025 6727948 ART08US PO8032 6690419 ART09US PO7999 6727951 ART10US PO8030 6196541 ART13US PO7997 6195150 ART15US PO7979 6362868 ART16US PO7978 6831681 ART18US PO7982 6431669 ART19US PO7989 6362869 ART20US PO8019 6472052 ART21US PO7980 6356715 ART22US PO8018 6894694 ART24US PO7938 6636216 ART25US PO8016 6366693 ART26US PO8024 6329990 ART27US PO7939 6459495 ART29US PO8501 6137500 ART30US PO8500 6690416 ART31US PO7987 7050143 ART32US PO8022 6398328 ART33US PO8497 7110024 ART34US PO8020 6431704 ART38US PO8504 6879341 ART42US PO8000 6415054 ART43US PO7934 6665454 ART45US PO7990 6542645 ART46US PO8499 6486886 ART47US PO8502 6381361 ART48US PO7981 6317192 ART50US PO7986 6850274 ART51US PO7983 09/113054 ART52US PO8026 6646757 ART53US PO8028 6624848 ART56US PO9394 6357135 ART57US PO9397 6271931 ART59US PO9398 6353772 ART60US PO9399 6106147 ART61US PO9400 6665008 ART62US PO9401 6304291 ART63US PO9403 6305770 ART65US PO9405 6289262 ART66US PP0959 6315200 ART68US PP1397 6217165 ART69US PP2370 6786420 DOT01US PO8003 6350023 Fluid01US PO8005 6318849 Fluid02US PO8066 6227652 IJ01US PO8072 6213588 IJ02US PO8040 6213589 IJ03US PO8071 6231163 IJ04US PO8047 6247795 IJ05US PO8035 6394581 IJ06US PO8044 6244691 IJ07US PO8063 6257704 IJ08US PO8057 6416168 IJ09US PO8056 6220694 IJ10US PO8069 6257705 IJ11US PO8049 6247794 IJ12US PO8036 6234610 IJ13US PO8048 6247793 IJ14US PO8070 6264306 IJ15US PO8067 6241342 IJ16US PO8001 6247792 IJ17US PO8038 6264307 IJ18US PO8033 6254220 IJ19US PO8002 6234611 IJ20US PO8068 6302528 IJ21US PO8062 6283582 IJ22US PO8034 6239821 IJ23US PO8039 6338547 IJ24US PO8041 6247796 IJ25US PO8004 6557977 IJ26US PO8037 6390603 IJ27US PO8043 6362843 IJ28US PO8042 6293653 IJ29US PO8064 6312107 IJ30US PO9389 6227653 IJ31US PO9391 6234609 IJ32US PP0888 6238040 IJ33US PP0891 6188415 IJ34US PP0890 6227654 IJ35US PP0873 6209989 IJ36US PP0993 6247791 IJ37US PP0890 6336710 IJ38US PP1398 6217153 IJ39US PP2592 6416167 IJ40US PP2593 6243113 IJ41US PP3991 6283581 IJ42US PP3987 6247790 IJ43US PP3985 6260953 IJ44US PP3983 6267469 IJ45US PO7935 6224780 IJM01US PO7936 6235212 IJM02US PO7937 6280643 IJM03US PO8061 6284147 IJM04US PO8054 6214244 IJM05US PO8065 6071750 IJM06US PO8055 6267905 IJM07US PO8053 6251298 IJM08US PO8078 6258285 IJM09US PO7933 6225138 IJM10US PO7950 6241904 IJM11US PO7949 6299786 IJM12US PO8060 6866789 IJM13US PO8059 6231773 IJM14US PO8073 6190931 IJM15US PO8076 6248249 IJM16US PO8075 6290862 IJM17US PO8079 6241906 IJM18US PO8050 6565762 IJM19US PO8052 6241905 IJM20US PO7948 6451216 IJM21US PO7951 6231772 IJM22US PO8074 6274056 IJM23US PO7941 6290861 IJM24US PO8077 6248248 IJM25US PO8058 6306671 IJM26US PO8051 6331258 IJM27US PO8045 6110754 IJM28US PO7952 6294101 IJM29US PO8046 6416679 IJM30US PO9390 6264849 IJM31US PO9392 6254793 IJM32US PP0889 6235211 IJM35US PP0887 6491833 IJM36US PP0882 6264850 IJM37US PP0874 6258284 IJM38US PP1396 6312615 IJM39US PP3989 6228668 IJM40US PP2591 6180427 IJM41US PP3990 6171875 IJM42US PP3986 6267904 IJM43US PP3984 6245247 IJM44US PP3982 6315914 IJM45US PP0895 6231148 IR01US PP0869 6293658 IR04US PP0887 6614560 IR05US PP0885 6238033 IR06US PP0884 6312070 IR10US PP0886 6238111 IR12US PP0877 6378970 IR16US PP0878 6196739 IR17US PP0883 6270182 IR19US PP0880 6152619 IR20US PO8006 6087638 MEMS02US PO8007 6340222 MEMS03US PO8010 6041600 MEMS05US PO8011 6299300 MEMS06US PO7947 6067797 MEMS07US PO7944 6286935 MEMS09US PO7946 6044646 MEMS10US PP0894 6382769 MEMS13US

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to fluid dispensing. In particular, this invention discloses a micro-electromechanical fluid-dispensing device.

BACKGROUND OF THE INVENTION

This invention is a development of a printing technology that has been developed by the Applicant. This development can be traced by considering the referenced patents/patent applications set out above.

Many different types of printing have been invented, a large number of which are presently in use. The known forms of printing have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 - 220 (1988).

Ink Jet printers themselves come in many different types. The utilisation of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. 3,596,275 by Sweet also discloses a process of continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)

Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et al. in U.S. Pat. No. 3,946,398 (1970) which utilises a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezo-electric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a Piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a sheer mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Manufacturers such as Canon and Hewlett Packard manufacture printing devices utilising the electro-thermal actuator.

As can be seen in the above referenced matters, Applicant has developed an ink jet printing technology that uses micro-electromechanical components to achieve the ejection of ink. The use of micro-electromechanical components allows printhead chips to have a large number of densely packed nozzle arrangements without the problems associated with heat build-up.

Applicant envisages that this technology can be used to dispense fluid. This invention is therefore intended to be a simple development of the technology that has already been the subject of many patent applications filed by the Applicant.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a micro-electromechanical device that comprises

-   -   a substrate;     -   a drive circuitry layer positioned on the substrate;     -   a nozzle chamber wall and a roof wall positioned on the         substrate to define a nozzle chamber above the substrate and a         fluid ejection port in the roof wall; and     -   a substantially planar deformable fluid ejecting member         interposed between the substrate and the roof wall and         configured to deform cyclically under action of a pulsed         electromagnetic field, the drive circuitry configured to         generate said pulsed electromagnetic field so that the fluid         ejecting member acts on fluid to eject fluid from the fluid         ejection port.

The nozzle chamber wall may define at least one fluid inlet to permit fluid to enter the nozzle chamber.

The drive circuitry layer may define a first planar electrode and the fluid ejecting member may include a second planar electrode which is connected to the drive circuitry layer such that an electrical potential can be set up between the electrodes, resulting in the fluid ejecting member being cyclically deformed to eject fluid from the fluid ejection port.

The micro-electromechanical device may include a support formation that extends from the substrate to support a periphery of the fluid ejecting member above the substrate, such that a central region of the fluid ejecting member is drawn towards and away from the substrate when the electrodes are activated.

The fluid ejecting member may be of a resiliently flexible member such that deformation of the member towards the substrate results in the build up of elastic energy in the member to enhance return movement and thus fluid ejection.

Complementary layers of hydrophobic material may be positioned on the ink ejecting member and the substrate to inhibit sticking of the ink ejecting member to the substrate. Instead or in addition a projection may be positioned on at least one of the fluid ejecting member and the substrate to inhibit sticking of the ink ejecting member to the substrate.

According to a second aspect of the invention, there is provided a fluid-dispensing chip that comprises

-   -   a wafer substrate that incorporates drive circuitry, and     -   a nozzle assembly positioned on the wafer substrate, the nozzle         assembly comprising         -   nozzle chamber walls and a roof wall that define a nozzle             chamber and a fluid ejection port in the roof wall, and         -   an electrostatic actuator that comprises             -   a first planar electrode positioned on the wafer                 substrate, and             -   a second planar electrode that is positioned in the                 nozzle chamber and is displaceable towards and away from                 the first planar electrode to eject fluid from the fluid                 ejection port, the first planar electrode and the second                 planar electrode being connected to the drive circuitry                 so that a potential difference can be applied between                 the planar electrodes to displace the second planar                 electrode towards and away from the first planar                 electrode,         -   at least one of the nozzle chamber walls and the wafer             substrate defining a fluid     -   inlet in fluid communication with the nozzle chamber and a fluid         supply source. Said first planar electrode and said second         planar electrode may define an air gap between the first and         second planar electrodes.

At least one of the nozzle chamber walls and the substrate may define an air path in fluid communication with an external atmosphere so that air flows into and out of the air gap when the second planar electrode is displaced towards and away from the first planar electrode.

The electrodes may have facing surfaces that are coated with a material having a low coefficient of friction to reduce possibilities of stiction. Said material may comprise substantially polytetrafluoroethylene.

Instead, or in addition, one of the first and second planar electrodes may have at least one projection that extends towards the other electrode to ensure that the electrodes do not touch when the second planar electrode is displaced towards the first planar electrode.

Said second planar electrode may include a layer of stiffening material for maintaining a stiffness of the second planar electrode. The stiffening material may be silicon nitride.

The roof wall may define a plurality of etchant holes to facilitate etching of sacrificial layers during construction.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a sectioned side view of one embodiment of a fluid-dispensing chip of the invention, in an operative condition.

FIG. 2 is a sectioned side view of the fluid-dispensing chip of FIG. 1 in a quiescent condition.

FIG. 3 is a perspective cross-sectional view of another embodiment of the fluid-dispensing chip of the invention.

FIG. 4 is a close-up perspective cross-sectional view (portion A of FIG. 3), of the fluid-dispensing chip of FIG. 3.

FIG. 5 is an exploded perspective view illustrating the construction of the fluid-dispensing chip of FIG. 3.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In FIGS. 1 and 2, reference numeral 10 generally indicates a sectioned side view of one embodiment of a fluid-dispensing chip of the invention.

The fluid-dispensing chip may include a silicon wafer substrate 12. A drive circuitry layer 14 is positioned on the wafer substrate 12. The drive circuitry layer 14 is in the form of a CMOS two-level metal layer that includes the drive and control circuitry for the fluid-dispensing chip 10.

A passivation layer 16 of silicon nitride is positioned on the drive circuitry layer 14 to protect the drive circuitry layer 14. A first planar electrode 18 is embedded in the layer 16. The first planar electrode 18 is of aluminum and is connected to the drive circuitry layer 14.

The fluid-dispensing chip 10 includes a nozzle chamber wall 19 and a roof wall 20 that define a nozzle chamber 22. The roof wall 20 defines a fluid ejection port 44. A fluid-ejecting member 28 is positioned in the nozzle chamber 22. The fluid-ejecting member 28 is planar and is aligned with and parallel to the first planar electrode 18.

The fluid-ejecting member 28 is positioned on a support formation 34 that extends from the passivation layer 16. The support formation 34 is dimensioned so that the fluid-ejecting member 28 is spaced a suitable distance from the first electrode 18. The support formation 34 is configured so that an air gap 40 is encapsulated between the fluid-ejecting member 28 and the first electrode 18.

The fluid-ejecting member 28 includes a second planar electrode 24 that is positioned in the nozzle chamber 22. The second planar electrode 24 is also of aluminum and is also connected to the drive circuitry layer 14. The drive circuitry layer 14 is connected to each of the electrodes 18, 24 so that a potential can be set up between the electrodes 18, 24 so that they are attracted to one another. A layer 26 of silicon nitride is positioned on the electrode 24 to impart a resilient flexibility to the fluid-ejecting member 28. Thus, when a potential is set up between the electrodes 18, 24, the fluid-ejecting member 28 is deflected towards the first electrode 18, as shown in FIG. 1. When the potential is removed, the first electrode 18 returns to a quiescent position as shown in FIG. 2.

A layer 32 of polytetrafluoroethylene (PTFE) is positioned on the first electrode 18. A layer 36 of PTFE is positioned on the second electrode 24, intermediate the electrodes 18, 24. This ensures that the electrodes 18, 24 do not stick to one another when the fluid-ejecting member 28 is deflected towards the first electrode 18. In order further to prevent stiction between the electrodes 18, 24, a projection 38 is positioned on the fluid-ejecting member 28. The projection 38 bears against the layer 32 to ensure that there is no contact between the layers 32, 36.

The nozzle chamber wall 19 defines fluid inlet openings 30 that are in fluid communication with a fluid supply so that the nozzle chamber 22 can be supplied with fluid. Fluid flows into a space 41 defined by the roof wall 20, the nozzle chamber wall 19, the fluid-ejecting member 28 and the support formation 34. It will be appreciated that this occurs when the fluid-ejecting member 28 is drawn towards the first electrode 18. When the potential is reversed, the fluid-ejecting member 28 is urged away from the first electrode 18 so that a drop 42 of fluid is ejected from the fluid ejection port 44. The fluid-ejecting member 28 could have sufficient resilience so that a reversal of potential is not necessary. In this case, release of elastic energy as the fluid-ejecting member 28 returns to its quiescent condition ensures the ejection of the fluid drop 42.

The roof wall 20 defines a rim 46 about the fluid ejection port 44.

In FIGS. 3 to 5, reference numeral 50 generally indicates another embodiment of a fluid-dispensing chip of the invention. With reference to FIGS. 1 and 2, like reference numerals refer to like parts, unless otherwise specified.

The fluid-ejecting member 28 has a peripheral portion 52 that is positioned between the nozzle chamber wall 19 and the layer 26 of silicon nitride. A corrugated annular portion 54 is positioned adjacent to the peripheral portion 52. A fluid-ejecting portion 56 defines a remainder of the fluid-ejecting member 28.

The electrodes 18, 24 and their respective PTFE layers 32, 36 are dimensioned to define the air gap 40.

The corrugated portion 54 is configured to expand when the second electrode 24 is displaced towards the first electrode 18. The silicon nitride layer 26 imparts a resilient flexibility to the corrugated portion 54. Thus, the second electrode 24 returns to a quiescent condition when the electrical potential is removed.

The nozzle chamber wall 19 is shaped to define four radially spaced fluid inlet supply channels 58 that are in fluid communication with the space 41. These allow fluid to flow into the space 41 when the second electrode 24 is drawn towards the first electrode 18.

The nozzle chamber wall 19 defines air spaces 60 that are in fluid communication with the air gap 40. These allow the passage of air when the second electrode 24 moves towards and away from the first electrode 18.

The roof wall 20 has a plurality of etchant openings 62 defined therein to facilitate the etching of sacrificial material used in the fabrication of the chip 50. The etchant openings 62 are small enough to inhibit the passage of fluid as a result of surface tension effects. It is important to note that the fluid-dispensing chip 10, 50 is essentially a micro-electromechanical systems (MEMS) device. A method for fabricating the device can readily be deduced from the description in referenced application no: U.S. Ser. No. 09/112,787 and in many of the other referenced applications.

Applicant envisages that the fluid-dispensing chip 10, 50 will be particularly suited for lab-on-a-chip applications. It can also be applied to DNA/RNA arrays, protein chips and sensing and dosing. The fluid-dispensing chip 10, 50 could also be used for drug delivery systems.

Numerous variations and/or modifications may be made to the present invention as shown in the preferred embodiment without departing from the spirit or scope of the invention as broadly described. The preferred embodiment is, therefore, to be considered in all respects to be illustrative and not restrictive. 

1. A fluid ejecting integrated circuit (IC), the IC comprising: a wafer substrate; a drive circuitry layer positioned on the wafer substrate; a protective passivation layer positioned on the drive circuitry layer; a nozzle chamber wall extending from the passivation layer and a roof wall positioned on the nozzle chamber wall such that the nozzle chamber wall and the roof wall define a nozzle chamber and a fluid ejection port in fluid communication with the nozzle chamber; a fluid ejecting member which overlies the passivation layer within the nozzle chamber and is configured to be displaced to eject fluid through the fluid ejection port; and a pair of spaced apart electrodes each connected to the drive circuitry layer so that the drive circuitry layer can create a potential difference between the electrodes, with one of the electrodes fast with the fluid ejecting member to displace the fluid ejecting member as a result of said potential difference.
 2. A fluid ejecting IC as claimed in claim 1, wherein the electrodes are in the form of one planar electrode embedded in the passivation layer and another planar electrode fast with the fluid ejecting member.
 3. A fluid ejecting IC as claimed in claim 2, wherein a support formation is interposed between the fluid ejecting member and the passivation layer to support the fluid ejecting member in a spaced condition with respect to the passivation layer.
 4. A fluid ejecting IC as claimed in claim 3, wherein the support formation is continuous and defines a sealed air chamber between the electrodes.
 5. A fluid ejecting IC as claimed in claim 4, wherein the embedded electrode is coated with a plastic layer which is located between the electrodes and whose periphery endlessly contacts the inside of the support formation.
 6. A fluid ejecting IC as claimed in claim 4, wherein at least one coating layer of silicon nitride is arranged on the electrode of the fluid ejecting member to enhance resilience of the fluid ejecting member.
 7. A fluid ejecting IC as claimed in claim 2, wherein a projection is positioned on the fluid ejecting member to inhibit stiction during deflection of the fluid ejecting member.
 8. A fluid ejecting IC as claimed in claim 1, wherein the nozzle chamber wall defines one or more fluid inlet openings through which fluid can be fed into the nozzle chamber.
 9. A fluid ejecting IC as claimed in claim 1, wherein the roof wall defines a raised rim which bounds the fluid ejection port. 